Lack of a Regulatory Function for Glutamine Synthetase Protein in the Synthesis of Glutamate Dehydrogenase and Nitrite Reductase in Escherichia coli K12

Abstract

Synthesis of glutamine synthetase (GS) in anaerobic batch cultures of Escherichia coli was repressed when excess NH,+ was available, but derepressed during growth with a poor nitrogen source. In wild-type bacteria there was only a weak inverse correlation between the activities of GS and glutamate dehydrogenase (GDH) during growth in various media. No positive correlations were found between the activities of GS and nitrite reductase, or between GS and cytochrome cSS2: both of these proteins were synthesized normally by mutants that contained no active GS. Although activities of GS and GDH were low in two mutants that are unable to synthesize cytochrome c552 or reduce nitrite because of defects in the nirA gene, the nirA defect was separated from the GS and GDH defects by transduction with bacteriophage PI. Attempts to show that catabolite repression of proline oxidase synthesis could be relieved during NH,+ starvation also failed. It is, therefore, unlikely that nitrite reduction or proline oxidation by E. coli are under positive control by GS protein. The regulation of the synthesis of enzymes for the utilization of secondary nitrogen sources in E. coli is, therefore, different from that in Klebsiella aerogenes, but is similar to that in Salmonella typhimurium.

The Chromosomal Location and Pleiotropic Effects of Mutations of the nirA+ Gene of Escherichia coli k12: The Essential Role of nirA+ in Nitrite Reduction and in Other Anaerobic Redox Reactions

“…Formate-nitrate oxidoreductase activity was determined with bacteria which had been grown for 16 h without aeration in 800 ml minimal medium (Newman & Cole, 1977) supplemented with 27 mM-glucose and 6.5 g nutrient broth 1-1 (Oxoid CM1) (Lambden & Guest, 1976). Cell membranes resuspended in 50 mMNa+/K+ phosphate buffer pH 7.4 were incubated at 37 "C with 40 mM-Na+ formate and 40 m -K N O , under a stream of N,.…”

“…Genetic methods. Lennox (1955) broth was used for conjugation and transduction experiments, as described by Newman & Cole (1977). Unless otherwise stated, a virulent derivative of bacteriophage Plkc was used to prepare lysates for transduction experiments.…”

“…A soluble cytochrome, cSS2, has been implicated in nitrite reduction by this organism because it is synthesized only during anaerobic growth and highest concentrations are found in extracts of bacteria in which nitrite reductase is most active (Fujita, 1966;Fujita & Sato, 1966. Furthermore, both the activity of the enzyme and the cytochrome concentration were high in extracts of a mutant unable to reduce nitrate because of a defect in the chZA gene (O'Hara et al, 1967;Venables, Wimpenny & Cole, 1968;Kavanagh & Cole, 1976;Newman & Cole, 1977). Other mutants with a NirA-phenotype were isolated on the basis of their inability to assimilate nitrite during anaerobic growth: these are deficient in both nitrite reductase activity and cytochrome c552 (Cole & Ward, 1973).…”

Genetic regulation of nitrate assimilation in Klebsiella pneumoniae M5al

“…However, synthesis of these anaerobic enzymes is independent of Ntr control (32), and anaerobic cultures actually excrete ammonia into the medium (6). Therefore, this does not represent a true assimilatory process, and E. coli does not assimilate nitrate or nitrite during aerobic growth (reviewed in reference 38).…”

Regulation of ammonia assimilation in ammonia‐limited chemostat cultures of Escherichia coli ML 30: Evidence of bistability

“…But it was also suggested that the GDH in E. coli is regulated differently (COLE et aZ. 1974, NEWNAN andCOLE 1977). The occurrence of the bistability in th.…”